Technical Field
The present invention relates to a stress-detecting element for detecting a shearing force that acts in a shearing direction and pressing force that acts in a direction orthogonal to the shearing force, a sensor module provided with the stress-detecting element, and an electronic apparatus provided with the sensor module.
Related Art
In the past there has been known a gripping device that uses a robot arm to grip and lift an object for which the weight and coefficient of friction are not known. In such a gripping device, it is necessary to detect a force (pressing force) that acts in a direction orthogonal to the gripping surface and a force (shearing force) that acts in a planar direction of the gripping surface, in order to avoid damage to the object and to avoid losing grip and dropping the object. There are known sensors for detecting such forces (e.g., see Japanese Laid-Open Patent Application Publication No. 2006-208248).
A tactile sensor described in the above mentioned publication has a structural assembly which includes a cantilever structure that extends from an edge part of an opening provided in a sensor substrate. The structural assembly is composed of a planar sensing part, and a hinge part for coupling the sensing part and the sensor substrate together. An electroconductive magnetic film is formed on the sensing part of the structural assembly, a piezoresistance film is formed on the hinge part, and the electroconductive magnetic film and the piezoresistance film are made conductive. In this configuration, an electrode is disposed on the hinge part and the hinge part is bent by pressure, whereby electric current generated by the piezoresistance of the hinge part flows from an electrode. The tactile sensor has a plurality of structural assemblies such as that described above formed on the sensor substrate, a portion of these structural assemblies being held erect in relation to the sensor substrate, and the other portion being held parallel to the sensor substrate. An elastic body is disposed on the sensor substrate, and the erect structural assemblies are embedded in the elastic body.